Someone has probably posted this before, but here is my experience with extending my python which was a few feet short

Went to local hardware store and picked up pvc tubing, a coupler, and 3 SS clamps. I chose to add the footage between the ball valve and solid vacuum piece

Total Cost:
5' x $0.84/ft
3 Clamps @ $1.30/ea - can go cheaper here if you don't want SS
1 Coupler @ $1.50/ea

$9.60 + tax. The nice thing about this though, is that a majority of the cost were the fittings, so if you need a longer piece, it won't be that much more. Wasn't a ton cheaper than the local pet store brand name extensions, 20' for $25. But saving any money nowadays should help. Plus I only needed 5' not 20