SFP Modules for Optical-SDI converters

Has anyone successfully swapped out the optical SFP modules in the SDI-optical converter? I'm in a pickle at the moment... using two SDI-optical converters across a 450' multimode fiber link. The signal is good 99% of the time, but does experience brief drop-outs. I've isolated the issue to the optical transceivers, but most likely because the factory SFP module is single-mode, which I'm using on multimode fiber.

I'd like to try and out multimode SFP modules into the converters to see if that resolves the issue. Please, anyone with info on what make/model SFP module? Thanks in advance...