Saw these in the Klingspor catalog.
They worth it  for a drill press sander?

https://www.woodworkingshop.com/product/RS30000/

It will get you started 
I bought one when I started

I started with the robo Sander too. The standard sanding sleeves became barrel shaped when installed onto the Robo Sander, The drum is rubber and swells a little when tightened against the sleeves..so i found some metal sleeves with 60 grit Tungsten carbide abrasive embedded into the metal sleeve they are about $80 from McMaster Carr I think.. I used that sleeve on the robo sander for about a dozen risers Before buying a Rigid combo Oscillating sander, at the time they were $200. I made over 20 bows with the Rigid sander, it was a pretty handy... I kept checking craigslist...found and bought a used Grizzly 6x80 edge sander and put a pattern sander on the end..   

I've been using the robo sanding drums I bough from Stu miller.  It works for me, but I've got the Grizzly edge sander now.  Which end did you make into a pattern sander, and how did you do it, if you don't mind me asking?

motor end. there are old threads on here with pictures.

Here ya go.

I just dropped my drive drum off to get the center of it turned.  I'm wondering where to get the bearing or whether I should just have them leave a collar on the table that's the same diameter of the drum. 

+ the thickness of sand paper

A rub collar or pin will be way cheaper than how  I done mine.
I think mine is .090 bigger than the drum and works good with 60 grit belts.

.080 on mine