I'm just getting back into bowling after a 15 year break.

The pro shop I used to buy all my gear from is long gone.
I used to get finger grips that were a little harder than Vice or Turbo grips.

I remember we called them poly grips, but I don't remember a brand name or where they came from. We would go one size small and then hit them with sander to give them a nice smooth edge and they would sand up flush with the outer surface of the ball. Also, they lasted longer then my interest in the ball. haha

Does anyone know what I'm referring to, and if so where can I find them?

Not looking for slugs.
The ones I'm looking for are oval shaped, no flat sides, no textures inside.
You can uses these without sanding them.

We sanded them to get a perfect fit on the fingers, and to keep them from getting torn if something catches on the outer edge.

There are also Contour Power Grips and Tenth Frame inserts.  Vise and Turbo are the most popular.

Not sure if these are what you're looking for but you can sand them and they're made out of silicone so they last a very long time.

http://www.viseinserts.com/fingerinserts_5.html