Make your own vacuum chuck
Many inquiries, below are a few suggestions.
The 'secret' to my 'FrugalVacuumChuck' is I placed a sealed bearing in the chuck which rotates and attached a semi-flexible tube into the bearing which does not rotate and extends through the headstock then attached to a vacuum source. With this setup a outboard adapter is not needed and therefore will fit 95% of all lathes.
The bearings that I used are referred to as 'motor grade', with double neoprene seals. You can search on line (Amazon) or buy from a commercial bearing supplier or Graingers. ID 3/8" x OD 7/8" x Width 9/32" Double Rubber Sealed Ball Bearing I shy away from the very cheap Chinese bearings.
3/8" OD x 1/4"IDpolyethylene tubing (Home Depot, Ace Hardware) (refrigerator water supply tubing) will fit into the bearing and will carry the vacuum through the headstock. If the fit of the tubing into the bearing is not a force fit, a wrap or two of scotch tape will snug it up. 3/8"ID hose from your vacuum source on the outboard side will slide onto the 3/8 poly tubing. In most cases you will not need hose clamps.
Links to 4 page illustrated instructions for suggestions machining your vacuum chuck and Seal PVC to workpiece:
VacuumChuckMachining Polyethylene 4-24-1.pdf
Illustrations below
My very popular - 3 Sealed Bearings,
Extension Tubes and Instructions
NOTICE: Bearing sets no longer available
Make a variety of different sized vacuum cups to be held with your 4 jaw chuck by turning a tenon on a dense hardwood block and common PVC couplers found in building centers and hardware stores. Detailed step by step instructions included. Starter set of 'foamies', (the gasket between PVC and your workpiece, not shown) included.
FrugalVacuumChuck.com