Should be possible if you can find a cheap pair of shifters - might take a little bit of time until they turn up though.
I'd go for Sora - I think they're the only Shimano ones to have a reach adjustment, which might be good for 11-year-old hands.
7-speed might turn up on the bay, but it's probably going to be easier to get hold of 8-speed, then either add an 8-speed cassette (if the bike is cassette rather than free-wheel), or just run it with the 7-speed block as the indexing will be close enough (cogs are 5mm apart for 7-speed, 4.8mm for 8-speed, so if you set it right in the middle, it's only 0.6mm out at either end. Sure, there's an extra click, but the mech limit screws take care of that - it's close enough for government work ...).
Should be possible if you can find a cheap pair of shifters - might take a little bit of time until they turn up though.
I'd go for Sora - I think they're the only Shimano ones to have a reach adjustment, which might be good for 11-year-old hands.
7-speed might turn up on the bay, but it's probably going to be easier to get hold of 8-speed, then either add an 8-speed cassette (if the bike is cassette rather than free-wheel), or just run it with the 7-speed block as the indexing will be close enough (cogs are 5mm apart for 7-speed, 4.8mm for 8-speed, so if you set it right in the middle, it's only 0.6mm out at either end. Sure, there's an extra click, but the mech limit screws take care of that - it's close enough for government work ...).