The regular sights don't seem as ideal as many folks would like them to be. There seem to the good Tech sights which a lot of people seem to recommend. So are there any other good iron sight options? Are there any rear iron sights that fit on a picatinny rail?
There are some combination Picatinny rail/rear sights made for the Ruger 10/22 like this one:
http://www.opticsplanet.com/williams-gun-sight-williams-ace-in-the-hole-scope-base-set-ruger-10-22.html
I have not used these sights and I don't know how easy the windage and elevation adjustments for the rear sight are. I have heard good things about the Williams Fire Sights over on rimfire central dot com. You might try asking the same question over there.
The stock Ruger sights do pretty much suck for anything other than casual plinking by people with good eyesight.
Some people really like the Nodak Spud iron sights. But they are more expensive than Tech Sights.
https://www.brownells.com/rifle-parts/sights/rear-sights/ruger-10-22-rear-sight-w-rail-prod56476.aspx?avs%7cManufacturer_1=nodak+spud+llc
https://www.brownells.com/rifle-parts/sights/front-sights/ruger-10-22-adjustable-front-sight-standard-barrel-prod42911.aspx
Some comparisons:
https://www.rimfirecentral.com/forums/showthread.php?t=500012