Having tried most of them on the market, the only one that made an appreciable difference was the one made by Nat Lambeth. Not sure if he still makes them.
I just put a longer aftermarket bolt handle and a kit sold on eBay by Desh industries on my lh Ultralite. Both together made a big improvement in the bolt lift. If I could get rid of a slight occasional binding on the forward stroke when cycling fast, the bolt throw would be perfect.
I have the Desh Industries kit for my Axis II, and it is a massssssssive improvement over stock. Its a simple couple of thrust bearings and a washer between them, plus trimming your spring a little bit - but the normally gritty bolt lift is completely gone. You can kind of get away with it with a hardware store hardened stainless steel washer, but the the thrust bearings are easily noticeably better than that. You may need or not need the spacer the kit comes with, or it may even need a little bit of sanding down... each gun is slightly different.
my axis ii with the lift kit,
I also put on a Glades Armory extended and knurled bolt handle, which further improved the bolt lift. The extra leverage is very helpful.
same as above, with Glades extended bolt handle
And while I think the stock bolt sleeve is perfectly fine, I did find a fancy flutted one for shiggles.
I don't shill products unless they absolutely work as advertised, or better. The Desh Industries bolt lift kit for the Axis does work as advertised, if not better.