It is not difficult to make and install new handrests for an Elise. Only basic woodworking skills, some suitable wood planed to roughly the correct thickness, a jig saw and some sandpaper is required. The stock handrests are only held on with two wood screws. The handrests can be removed and reinstalled without damaging the concertina so this is a reversible modification.
Personally I think that hand rests should be somewhat higher in general and much higher under the forefinger than the little finger, but that is not possible on a budget concertina like the "Elise".
I found that the left hand stock handrest was OK, but I made a wider and taller handrest for the right hand side. I will try a sloping handrests as Inventor suggests - that had not occurred to me.