I have 4- 10.5" pistols and all of them have the Holosun 503FL, and I prefer the circle dot to just a plain dot, but like having the option. I use the
Absolute Co-witness mounts (LHM-2AC) from Primary Arms. They do have a lower 1/3rd option as well. PRO-tip, buy them from Primary Arms Ebay store, they didn't charge me shipping! I did try a
Primary Arms MicroDot ($89.99) on my 9mm build, but found that you had to crank it up really high to see it in bright sunlight, so it was replaced by the 503FL. Now the Primary Arms sits in a box until I find a new home for it.
Got all of the Holosun's from Optics Planet, the first one was a price match from Lanbo's Armory, the rest were even cheaper on sale and they often run 10% off coupons, there is a member here you can PM to get a discount code, but don't know who that is.
Optics Planet currently has the 503FL on sale for $149 right now, see if you can find how to get a discount code for arfcom members and get an even better price. FYI, the 500 series models should all have the option of dot/circle dot. I like this model because of the flip caps and battery mounted on the right hand side, vs. underneath the mount. For $135 that's a pretty good deal.
Holosun 503FL for cheap!
(I have no affiliation with any of these companies and receive no benefit).