For 4" K frame hoslters, there are so many options. Simply Rugged is good, Bianchi 5BHL's are great, but if you are seriously penny-pinched, go to ebay and you can find 20 for sale at any time for $10 or less. Do your homework, and some of them are classic designs dating back to the '20s. I insist upon a thumb safety, personally, so we are on the same page.
Just some cut-rate shopping advice - there are millions of these K guns out there, and millions of holsters. Search for what you want -there's no need to settle for something you don't like or if you are cash strapped, to pay very much.
My very favorite OWB belt K frame holster is the "Roy's original" pancake. They are out of business (Roy died a while ago), but they are fantastic and available used frequently. Here's a 2.5" with the pancake.
For woods carry, I really like the WWII classic "Tanker" or "Pilots" holster. These are great and functional when you don't need to conceal. Pacific Canvas and Leather imports a cheap Chinese knock-off for $40 (Cabela's sells it). It will hold a 66 well. I use if for both a 10 or a 66 in 4".
1) OWB Roy's Original
2) WWII Tanker style, Not a 4" Model 10, but a custom job made to look like it: