Well, finding them is the first thing because they certainly aren't as plentiful as they used to be. Get onto the banner advertisers and check them out. Posting as you did might find someone with some of those parts available.
As for not being drop in parts as Sunray mentioned that is a very BIG MAYBE. I have never had a problem with that on several different rifles. But you never know it is easily possible.
There are also other parts you will need to procure as well, such as firing pin, proper extractor and striker with spring. Most common bolts that are acceptable for the Mark of rifle you are converting should work just fine.
I saw a very neat little No5 that had been converted to 22rimfire recently and the only thing done was to sleeve a worn out barrel with a commercial liner, replace the regular firing pin/spring with an appropriate striker/spring as well as a firing pin/bolt head/extractor. He had an epoxy filled mag as he used it as a single shot. To make a repeater out of these rifles requires a lot of smithing and a lathe.