Adjusting Membership Fund

We are an organization with multiple locations to sell memberships and we like to track these different channels through different Membership Funds. Now that we have more membership gifts coming in online, we still want to credit our specific sites for the membership if we can clearly connect the sale to that site. Adjusting each contribution to put the payment on account and create a new contribution after the initial gift is made is not ideal, but the only solution we have found to change the fund on a completed contribution. Does anyone have any other work around for this? Or maybe this will be included in an update? Thank you!!