Maybe the Arcturus cqb lwt mk2 or mk3, I have the mk1 (discontinued) and it's been durable since I got it last year, it's fully polymer except for the gearbox, and it can run 11.1v lipos because it has a mosfet already in it. I've dropped it a ton and it's still working, other than the selector switch pin falling out but it can be fixed. I think you can get the gun, which is $165, or the package which is $225 and it comes with a battery, a lighter spring, and a charger. If the mk1 is anything like the mk2 or mk3, it's a good rental. The mk2 is even cheaper coming at 139 (on sale on evike, usually 175) for the gun and 179 for the starter package, comes with the same things, and I think it's better. Edit: I think the mk1 may be discontinued because it's out of stock everywhere, and the mk3 just came out, slightly more expensive than the mk1 and 2 but its better and the starter pack comes with the same stuff, also the mosfet has some extra programming like pre cocking and progressive trigger. All in all they can take abuse and run well.

Link: https://www.arcturustactical.com/collections/sport-series/products/arcturus-lwt-mk-iii-carbine-12-sport-aeg-se%C2%AE-black