Well, the 4mm was too small but this fit perfectly: Borosilicate Glass Tubing 5MM Outer Diameter. I have like a zillion feet of it as it came in 1ft lengths as a pack of 10.
The O-rings mentioned were a bust, though I did use one on each side then used
@komet163b suggestion of using twisted Teflon tape. One side seems perfectly sealed and the other is going to weep a little if I don't try it again. Needless to say if I break the glass again I'll have lots glass tubing in stock!
Now I have to figure out a heater, got my bother's Jensen in today and it is way to long.