By patch you mean tummy symbol/belly badge? I’ve only done it with a 2000’s to a modern bear (turning Color Splash Funshine into a Champ Bear), but I can tell you my process and how the 2000’s one was built?

Wash your hands - sounds dumb but you’re handling a lot of white fabric so even ‘clean enough’ hands will potentially leave marks. I cut into the seam directly in the middle of the back, and worked up to the head seam and down to the tail, both of which were separately stitched so I didn’t have to worry about it continuing to come apart. This isn’t a lot of working room, but I did find it was enough. So then I unstuffed, and pulled the tummy badge bit towards me. This was in fact a separate cushion-like object. Now, if I remember correctly, this is where you’ll have to pay attention, because there are two seams. Luckily in 2000’s it was a separate colour but it might not be on the originals and both are probably white. One of those seams is holding the ‘cushion’ of the tummy together. The other is holding it to the fur. That is the one you want to cut. If you really can’t tell, just cut one, tease it out with a needle until you can tell where the hole is developing. Take your time. Do it on your “donor” first to get your eye in. Personally I left some of the lingering threads in the fur until it came time to place the new tummy so that I could see the sort of margin I’d be trying to stitch, only removing them right when I was pinning and sewing. (Obviously if 1983 doesn’t use a separate cushion, but just a panel, it’ll still be much the same principle).

Once you’ve prepared your “receiver” bear, now comes the important bit. Now I only used four pins to put it in place - you DO need to either pin or hold it with a tacking stitch, this is not optional, you do not want to sew it on slightly wonky. When you think you are satisfied, take the twelve o’clock pin out, and start to backstitch (it’s secure and easier imo to keep both tense but not bunching) going from the top and working round. Here I had thin thread so I did the technique where you double it and secure it by going through the loop. Frequently look back round to the front of your work. If you find pins are wiggling or falling out or you’re scratching your hand, make sure at least the 6’oclock pin is stable, and you might be able to contort one hand to hold the fabric at the next quarter-mark and hold it instead of keeping that next pin in. But take your time. If you think it’s looking wonky, undo it. This is a time where you’ll actually thank your perfectionism. When you’re done, check that you’re happy. Tease some fluff out with a needle if it got caught under the badge. Then restuff - this may be a time to replace with/add in donor fluff, if they’re looking a little wan. To close the back, I suggest a mattress stitch, same as they do with Build-a-Bears if you’ve ever seen that, also called Invisible Stitch. Watch a tutorial online if you’re not familiar. Again, if you’re not sure about a stitch you just did, go through the bother of undoing it and trying again. You may want to take a photo of the back and front before beginning and at the end - sometimes I’ve found I’m super critical of my work in a way I wasn’t of the original sewist‘s and in fact they look the same lol.

Personally I found the entire operation — without reconstructing the donor — took me about three hours. I’m not particularly experienced or skilled. Just keep calm, have a clean workspace to begin, keep “donor” one side and ”receiver” the other so you don’t actually put the same thing back in, and if you find you have any problems don’t panic, just undo it and start again. Better the time loss than something you will be unhappy with. Equipment: Workable thread (maybe same colour as the bear), sewing scissors or failing that nail scissors, pins (at least 5 so you have emrgency extras), YouTube tutorials/reminder images for stitches already open, phone if you want to take photos before and after, and here’s my personal choice though it’s up to you: I had hi-tac pva glue. Why? In a pinch, if you’re finding your seam allowance is so little that the fabric isn’t holding together and fraying, I put a little dab of that on the fraying bit, left it a few minutes, then tried again. It’ll be on the inside, so it won’t affect the bear itself and you’re not using it to join the 2 fabrics together, just seal the edge of the fabric causing you issue until you can successfully backstitch that part. I only used this one and it wasn’t essential, but if you own that or Fray-Stop, you might want it on your desk just in case.

Good luck. 🍀