Well, yeah, a bellows is the ultimate way to go, if one can find a decent one, not costing a whole lot more than an extension tube set, that is of good quality and won't fall apart in 10 years.
A sliding/telescoping tube design could also work.
Both Accura and Vivitar (like the one above) are very good quality and extremely inexpensive, even if they did fail they're cheap enough that it doesn't much matter. Pentax made very good bellows also, which go for a bit higher price. Thought not having AE which is a pain if you're into bugs. But yes. Autobellows are $$.
Of course if I'm looking at this correctly, you wouldn't have AE here either, would you?
There are also some AMAZING looking soviet-built bellows out there. These are all in m42, ofcourse, but that's not a problem if you use enlarging lenses (Rodagon 50/4.0 above). I'd post samples, but my hard drive failed last night.
The PB-4 is the one I used to have. It's the one that crumbled to pieces a decade ago.
I did look today at what B&H had for various bellows. There are a few out there and I may get one. But I still want to be able to mount my existing lenses on it, which still include a few Nikkors. But I have one adapter, now. I just need to get a special tool to put it on properly.