Is your Shure M55E a genuine single coil cartridge, or is it a stereo cartridge with both outputs connected in parallel? I ask because I can find no reference to a Shure M55E MONO.

The Miyajima and Ortofon SPU MONO cartridges are definitely single coil designs, despite having four pins on the cartridge body.

Another single coil MC cartridge you might like to try is the Denon DL102. This has two long pins on the body, so you can 'piggyback' the two pairs of headshell leads.