First, use Work Orders not Back Orders.
Second, create a non-inventory item (or several) to use for special orders. Something like SPECIAL or SO-DEPT where you create an item for each department.
I have created a macro that does the following: Ctrl-F2 (Work Order), Shift-F9 (Details), 'SO', , 'SPECIAL ORDER', Alt-O (Override Deposit). I then associated the macro with a custom button through an add-on I got from this forum. Now I have a custom button for Special Order that the cashier can click before entering any items (or later, but it's best to do it right away). If you're interested in the add-on, look here:
formatting link
and download everything in the AltKeys folder. The 'Read Me' file explains everything. When you create a work order, use the non-inventory special order SKU for items not in the database. Have the cashier enter as much info as possible into the description. Make, Model, Color, Style, etc. Enter the actual selling price. You can take a deposit (or not). You can set a due date for whenever you expect the merchandise to be available.
You can then generate an Open Orders report (regularly, on whatever schedule suits you) filtered for Reference = SO and sorted by Due Date. I have a custom report (two actually) for this sort of thing. If you're interested, I'd be glad to e-mail them to you.
A manager can generate the report, review the work orders on the report, create the items, generate the POs, then recall the work orders, add the newly created items, delete the non-inventory items, and save the changes.
I'm interested to hear other solutions to this problem, as I am always looking for a better way.
HTH, Tom