I was looking at getting an optics mount for my Ruger GP100 and was wondering what all. The options were out there.  I was looking at putting either an RMR or MPS size optic on it.  The only mount I could find was from allchin gun parts. Mainly this one below.

https://allchingunparts.com/products/ruger-gp-100-rmr-holosun-c-mount.html

Are there any other good options out there that I haven’t found yet?  Or is this really all that exists?  Thank you all for looking.

Tons of mounts available. You need to decide on optic.
Vortex, EGW, Weigand, etc, all make mounts, just like Allchin.

I have that allchin mount with a vortex venom on a blued 6” gp100.  
Looks great, low profile, and works well.

Also kinda matters which model you have.  The GP100 has different styles of rear sights.

To answer the questions so far, I am leaning towards either an MPS or ACRO.  I have several MPS's and love them so I am probably leaning that way.  I said RMR optic as I was debating on the RCR but I feel it will be unobtanium like the ACRO was/is.  
My GP-100 is the 5 inch 10mm with adjustable sights.  It isn't the match champion model but the Lipseys exclusive that was offered maybe 5-6 years ago.  Below is a link about the line up if that helps.

https://lipseysguns.com/lipseys-exclusive-ruger-gp100-in-10mm-completes-quartet-with-fourth-offerings-in-the-series/

Hope this helps, I am leaning towards the Allchin mount with an ACRO adapter, but was curious if there was any direct mounts like below. (I know it is for a S&W but was hoping someone made one for the Ruger's.)

https://www.apextactical.com/apex-revolver-optic-mount

I installed a WEIG-A-TINNY style scope mount on my Ruger GP100 .357 6" barrel revolver.  Unfortunately, it does not look like they have a rail for a 5" barrel GP100.  Thought I'd mention it for anyone else looking for a mount on the 4", 4.2" or 6" GP100 versions.  Installation is very easy.
 
https://www.jackweigand.com/Ruger-GP100-Scope-Mounts-No-Drill.html

I just put an EGW mount for a Sheild/J-point pattern optic on my Redhawk.  Same mount fits the Blackhawk, Super Blackhawk, Gp-100 (adjustable sight models only).  They make them for several different mounting patterns.

I recently put an EGW on my 4” .357 GP100 w/adjustable sights. Optic is Holosun 508T. Went on with no problem, fits nice and tight. Zeroed it easily, fired 55 shots of full-tilt .357, and 5 shots of Critical Duty .357 (much milder). Like 25 or so .38 wadcutters, also. It shot well at 25yds.

I’ll revisit this thread if it loses zero, shotguns at 100yds, or smacks me in the forehead.

Please do!  I would be interested if anything happens to it.  I will probably be buying everything for the revolver early part of next year and will post pictures when I get everything assembled.  The only time I ever had a red dot come off was when my wife was shooting the pistol and it smacked straight into the forehead.  (We laugh about it now, but the conspiracies were flying that day)

Hasn’t launched off the gun or lost zero yet. I haven’t shot a lot of .357 lately, though. Probably will shoot another few hundred in a week or two.