Glasswork is really not that hard, i have an artist friend who makes artworks from glass, has the furnace and does all sorts of weird and wonderful things....
Its the accuracy required to make lab gear which is hard...

He isnt very science tuned (not many artists are) so i decided a while ago to see if he could make a RBF (simple to make a round bottom bottle in his eyes) showed him a drawing and he went to work....

Didnt turn out to bad, was right shape, even all the way around... but its hard to get volumes, ended up (after cooling and setting) fitting in 2.37L of water to the brim.
The only problem with it was that the walls were not thick enough (i didnt specify this when he was making it... doh!) and the rim could not be ground to a certain socket size as 1) the glass was to thin and 2) he doesnt have that equiptment.

So if someone can learn to gring the glass joints and find the equip to do it properly, easy, a normal glassworker can make it provided you specify the requirements of it...

-AC

This chapter on glass blowing by Hershberg, found in Fieser's Experiments in Organic Chemistry shows how to construct a condenser from borosilicate glass, bends,  grinding it et cetera  

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000519514-fieser-hershberg.djvu" target="_blank" title="Download this file">

If the only way for you to get flasks is having them custom made then you are fucked, because that simply is too expensive.
No glassblower produces ground joints themselves anymore, they buy them and then put them on whatever glassware when repairing shit or building specialized equipment.

Stainless Steel