The Glenfield 22 model 75 is the same as the Marlin 75. It was made for Sears and the parts probably can be obtained from Marlin In New Haven, Connecticut. This site has parts for the Glenfield model 75. http://www.gunpartscorp.com/ I have them. www.countrygunsmith.net
Your Glenfield Model 25 is actually a Marlin Model 80 with sling swivels. According to leverguns.com Forums all of the Glenfield rifles were numbered right along with the Marlines. According to http://armscollectors.com/sn/marlinlookup.php your rifle was manufactured in 1973.
The Glenfield model 25 wasn't a Marlin, so determining what it actually is is not easy. Obtain a copy of Modern Gun Values and try and determine the actual manufacturer. A Glenfield version is typically worth 75% of the manufacturer's value.