Clearidge Ultra RM 3-9x32 AO.
Many reviews on Rimfire Central
I have these on two of my .22's, and they are very good scopes. especially for the coin. they are larger than the leupold rimfires, though, if we're talking about a "small" scope for a .22.
and the post above about having parallax set for 50 is an important point. just slapping a regular Leupold or Redfield 2-7x32 or 3-9x40 on a .22 can be done, but i've found it to be very frustrating for target shooting at 50 because the parallax on those scopes is set for 100 yds plus.
bear in mind that the Leupold EFR and the clearidge both have adjustable parallax, which is a nice feature.