It sounds like you have an open mind about rechargeables and for that I applaud you. Depending on what you are used to, rechargeables can have a lot of (bad) baggage associated with them. The Lithium Ion rechargeable cells that are in new flashlights are nothing like the old NiCd stuff that I grew up on. Even the newish NiMh has a hard time keeping up with these cells.
When I discovered that the 18650 cells that the BLF A6 uses are the same ones that my laptop and good new cordless tools are using, I felt better, and having used my A6 for the past 2-3 months, I can honestly say that I am NEVER going back to AAA and AA cell lights for my EDC. I’m not getting rid of all my old AA lights, but I don’t worry too much when I give them to my daughters for Girl Scout camp-outs. If they come back, good. If not - meh, oh well.
For the relatively low investment of around 40-50 bucks, you can get a good starter (white) light, a couple 18650’s and a starter charger that you could use in the future in your truck. If you are not happy with the run time, give the set to an employee. I can’t help much with UV, but there are several people here who can. I do know that there is a Convoy S2+ UV light that is just now coming out. The Convoy S2+ series gets high marks from just about everyone who reviews it, and there are MANY people here who have multiple S2’s.
Happy New Year from a relative newbie, and welcome to the insanity.
If you want to start with a white version rather than going straight to UV, you can pick one up for $17 in several different anodized colors.
I will warn you that if you are shopping around for a better price, make sure you are buying a complete light and not a HOST, which does not include the LED or driver circuitry.
I just Finished making 2 UV lights using Simons s2 Host + and his 1A drivers these visible light filters and these emitters by led4power for work and have been having so much fun grossing out my family and friends with pets and carpets. I have made UV lights before and have had limited success in this regard even using more powerful emmiters but the visable light created always made it difficult to see the forensic stuff. With the visable light filter lens in place and a dark room EVERYTHING is visible with these lights. But watch out for ancillary costs my wife made me run out and get a wet carpet cleaner the next day which cost several times what the light did!
edit I should note that these emitters put out substantially more UV than anything else i have used with the exception of the LZ1 and even then the output is close enough considering the cost difference. Cures UV adhesive in seconds and turns my auto darkening glasses fully dark in seconds as well. I use them for finding the Tin side of glazing and to identify florescent tracer dyes at work.