The blades aren't available from Sears, nor anywhere else I can find. Harbor Freight might have had something that might work a few years ago, but not anymore. And they don't look like they'd be easy to sharpen. So if anyone has a source please post, otherwise my tool is worthless.
The blades are the same as used on a name brand jointer that I can't remember at this moment. I'll post it if I remember, but I know you'll have no problem getting them. I was going to replace mine so I found out quite a while back what it would take but I decided I would have them sharpened instead. Sorry, not much help.
I was actually in a Sears store over the past summer, looking at some of their power tools. They do carry a 4 1/8 inch planer and the replacement blades look identical to the ones for this model. I compared my old blade to the ones still in the package and I can't tell the difference. I didn't buy them because I'm not sure if I need to replace them yet. I beleive they were around $12.00. If you search for them online, the picture might show the blade with 4 holes. The actual blades that I found do only have 3. Matter of fact, here's the link: http://www.sears.com/shc/s/p_10153_12605_00922993000P?keyword=4+1/8+inch+jointer
Also, I am still in need of the manual if anyone happens to run across one. Thanks.