If it's the V175 tubs, it's not that they're all that hard to find exactly, it's that for a lot of people they tend to be seasonal so you have to jump on the chance to buy them when you can to get them locally. They would certainly do a smaller locality boa for life though.
As for BRB's, I think they make a good starter animal as long as you understand their humidity needs and get your caging set up appropriately for it. Get that set up and keeping one should be a piece of cake.
I actually have some of the V175 tubs and am planning in the near future to build a rack to hold them...it's purpose is going to be for housing my adult breeder pairs/trios of BRB's, one of those pairs being a 6' male and 7.5' female and I don't see them having any issues due to not enough room for them.