It turns out there's actually a red rupee available by digging just to the left of the door into Link's house. This respawns every time you re-enter the area, which is easily achieved by going in and out of the house. So the plan is to collect 900 rupees here, then head into the town and swap them for 90 mysterious shells. At first I was going to stop there and try to get the figurines with just that (spend 15 shells per attempt, resetting until I get a new figurine), but then I realised that it didn't actually take me that long to get the shells. And with only six left, getting enough for guaranteed success on every one won't take much longer.
I guesstimate it at being less than 4 seconds per red rupee, and did the mental arithmetic while picking up the rupees. It takes 45 red rupees to get 900 rupees. That's 180s or 3 minutes each. So, do this six times to get 90 shells to use for each figurine, taking a bit more than 18 minutes... actually, that's only 540 shells so let's go round again and make it >600 shells so I can use the maximum number per figurine. Call it under 25 minutes total, and I can *finally* get into the music box house.
Now to deal with those dratted Cuccos...
Have I told you how much I appreciate your continued patronage?
Because I do.Stockwell, Minish Cap