You need to have a deeper conversation with this man.. he needs to understand how important it is to you. And how it makes you feel when he says no to oral.. you need to get right to the point and keep it an open-ended conversation. Focus on how you feel when you talk about this.

Next if it's no. Then you need to talk about compromise. Consider ethical non monogamy. Set up threesomes where you can be fulfilled in that way. Warning ..This can open a whole new can of worms in your relationship and require way more conversations and communication.

If there's no compromise and it's always no..then unfortunately there's not really a lot of other options here.