For slices, we use a slice anchor from Warner Instruments:
Specifically order number 64-1411, Model number SHD-22F/15. I think your ideal harp may depend on the size of your recording chamber so I’d take a look at their whole selection: https://warneronline.com/images/image_enlarge.cfm?image=Series%2020%20and%2040%20slice%20hold-downs
Hey @liz and everyone else. An update. I got the
STAINLESS STEEL SLICE HOLD–DOWN FOR RC–26G CHAMBER
It was definitely worth spending the money ($63, not much) to get a properly sized harp for the chamber I use R26-G. It fits perfectly and holds the slice down, and the 1 mm spacing is very adequate to advance a pipette to a spinal cord slice.