At the Joint Math Meeting, I set up a huckster table, selling Klein bottles. I put up a sign, "SPECIAL BANARCH-TARSKI TWO-FOR-ONE SALE". About the only place I could pull off that stunt...
I've tried several times to make a Boys Surface. It's really hard to do. Bending tubing around its own radius - really challenging. Easy to kink, difficult to get uniform. I've commissioned my friend Lucas Clarke and he's had encouraging results; alas but I've seen too many shards of 30mm diameter borosilicate tubing.
Will keep trying...