It shouldn't cost anything. Don't think you need a new e-store provider.
Just leave the product up but change the text in the item description to reflect it's temporary status. At least then the product exists as an option. We could still read about it and budget to purchase when available.
Can't be too hard to edit the text of the description.
For instance...currently the rubber traction belts seem unavailable.
When trying to buy one we get this
Attachment 79345
Like they don't exist.
obviously they are out of stock but I only know that from reading the forum discussions.
If you can't give us the part right now at least let us look at a picture of it with the specifications and price while we wait.
No cost and improved customer satisfaction.