We have Boathouse Discount Marine in FL, two stores in Jacksonville and one down in Melbourne, and I see they're open for a few hours on Sunday. Seems MarineMate is similar, hope they were able to help.
Thought of a couple MiniStarter comments:
First, they last a very long time. They may not look like much, but they'll run for years. I was used to the old Delco-Remy starters, direct drive with field windings. All manner of parts were available for those. Solenoids, Brushes, Drives, Bearing Bushings... Mini's aren't like that. Gear Reduction, and the last I heard, only a Solenoid was readily available. But one ran on the 5.7 that powered our boat from 1996 to 2015.
Second, another common failure can be a rusted shaft at the Drive. Starter would run but not engage. That little less-than-an-inch the drive spins out onto when the starter's cranking gets rusted and the drive can't spin out to engage the flyweel. This happened to me twice. On the 5.7 mentioned above, I pulled it off and saw the problem. Since I didn't have a spare then, I cleaned the shaft off with emery cloth, put a little oil on it and reinstalled. Called a starter shop and they said a new drive wasn't available for that starter. Left it installed and didn't work on it again for 10 years and 1000 engine hours.
So, if you hear the starter running as a motor but not cranking the engine, pull it off. Try it again on jumper cables out on the dock. No bilge sparks please! If the drive isn't jumping out into drive position, see if that little shaft section is sticky or rusty. If it is, make it clean and bright, put a drop of oil on it, and try it. If it now works, just reinstall it. When that happened to me, I didn't work on it again, but I did get a spare. That same starter also became a spare.
Second failure, same thing on the reman engine called a "357." Spun but Drive not extending. Swapped the spare on and cleaned up the failed one later. Now it's the spare. Even though it has only 150 hours on it, I'm satisfied to use the 1500 hour one.
So... if you don't have to turn a starter in as core on a reman, clean it up and keep it. It'll make a good spare in most cases.
Oh, collect a couple spare starter bolts for your spare. They seem to be attracted to the Bilge...