3M is a good tint, not necessarily comparable to Huper. 3M is a tinted tie film and Huper is a ceramic based tint. Huper will reject alot more heat than 3M.
What are you looking for in a tint? Heat rejection or the 'look' of it?
If you are just going for look 3M will be fine and you can get it dark. If you want the highest heat rejection Huper is the stuff.
To my knowledge the company did not go bankrupt. The people that told you that they went bankrupt, did they try sell you 3M or Llumar by chance????
Huper is hard to find. They won't distribute it to just anyone. If you want it keep looking, you will find it. Email the company via their webpage if you have to.
Bottom line, 3M is a good product to make your windows look dark, Huper is a great product to reject heat (Huper isn't a super dark tint).