[oredith]

the DIY in me would want to just make my own.

amazon sells:

• 1" Delrin balls @ 10 for $8.95
• 1/4 x 20 t-slot bolts @ 5 for $4.42

that means if you have a drill press and a 1/4x20 tap ($6.02 from amazon, or $13.99 for an entire set from Harbor Freight), you can make 10 of those things for $1.78 each.