It's true, given the fact that he likes 'The Bluebird', 'Last Night' would be a nice choice.
But the affordable firsts of this one usually aren't signed. If your friend is only after a first edition and cares not about the autograph, this doesn't matter. But I'd bet, he'd prefer a signed book. A signed first of 'Last Night' would cost, I guess, around 400.- plus USD. Right? (There are collectors on the forum who know the prices much better than I do - hope they jump in here!)
Having had a very quick and sloppy search through ebay, I've found affordable signed firsts of 'Post Office', 'Hollywood' and 'Pulp'. Haven't checked their condition though, so I don't recommend them here by giving links.
'Post Office' is a classic. While 'Pulp' is important being his last novel (and together with 'Screams from the Balcony' it's the last book he ever signed personally!). - btw: there's a signed first of 'Screams' on Abe for under 200.- and you can usually bargain with the sellers there.
I'm not the #1-source of information on that matter here on board, so I really hope the experts contribute.
Anyway, if you buy him a collectible - ALWAYS make sure to buy him an additional cheap trade-copy of the same book as well. He should Never need to actually use a collectible for reading purposes!
Since he doesn't have any Buk-books by now, maybe chronic's idea about the broadside combined with a nice pack of several books (trade-copies) would suit his needs best..?