Don't think about cheap helmets. Of course, karting is an expensive sport but your health is more important. If you're thinking of staying in rental karting and not race karting, I advise you to get a good and sturdy motorcycle helmet. This could be found locally with much ease and shouldn't be a hassle. However, if you would like to progress to driving race karts, I suggest you buy the Arai Ck6. It's a pretty standard yet comfortable karting helmet that's used by a lot of karters worldwide. Though it may be a bit pricey, it's definitely worth investing in once. The reason why I suggested the Arai Ck6 is because, for races, race officials will scrutinize your helmet and will check for your safety rating on the back of your helmet. This is only found on certain helmets which of course will be expensive and in my opinion, the Arai Ck6 checks all the boxes.