As Rusty said,tell your friend to bite the bullet & buy a new cam or give him several options.
1-tell him he's getting fat & lazy and borrow/buy a new or used push/self propelled walk behind mower,after 2-3 times of that I'll bet he'll come up with the $$ for cam real quick.
2-tell him to locate someone that has sheep/goats & rents them by hr/day & turn them loose in yard.
3-call several local lawn mowing services & see what they charge by wk/month.
4-the other side of the coin is your friend is "playing you" in that he's to lazy/ignorant to locate cam/gasket himself,give him the pn's for cam/gasket & let him locate and buy a new/used cam,right now you're doing all the mech work,research & leg work trying to locate cam while he just sits back whining,this can strain a friendship to the breaking point.IF it were my call & he doesn't want to spend the money for a new cam I'd put eng in a cardboard box & give back to him with a message-when you locate/buy a new/used cam give me a call & I'll repair eng.