Hallo Dianeinboston,
There is no established way on imslp how to deal with something like this score, which seems to be very rare. Until now some users that had purchased microfilm/photocopies/scans for their own use have generously uploaded them. But to my knowledge no one has asked about the possibility to "spread the cost for a scan" among interested imslp users (would also be difficult to find a payment mechanism).
Very few libraries will put something on their scanning schedule by request - I can think only of Sibley and John Farrington
. Sibley has federal grants, but other libraries must recover some of their costs.
However, SBB allows copying out-of-copyright materials back to currently 1850, if in decent condition. Since the in-house-copyshop charges only 6 cents per copy (minus a 10% heavy user discount), I have copied the occasional rare item if its just a few pages, then scanned the copies and uploaded to imslp. (Do-it-yourself scanning may be available soon at SBB).
The official scanning service by SBB is much pricier: There is the unfortunate 10 euro order fee plus the first 10 scans at a higher price, whereas additional scans are 30 euro cents per page for the basic 300 dpi color scan, and you can combine many titles into one order - and everything they scan is then put online within a few months.
So you have to consider your options: Is it likely the work you are interested in will be scanned because of another request, or because it is part of the SBB focus (C.M.v.Weber, Quantz, it seems, in addition to Bach-Mozart-Beethoven). Or do you really want the scans badly. For the Dancla, at about 35 pages this would be 10.50 euro if added to another scanning order, but about 25 euro if ordered separately.
It may be worthwhile to consider a "SBB-wishlist" on imslp, and if someone is able to add an item from the wishlist to his order that would save a lot - but I am not sure how workable this is, as even short works cost real money.
(P.S:: I am not a violinist (I play the oboe), so I have no use for the duos myself)
, I will scan the photocopies I made and upload soon