Hello Guy,
Unfortunately, Oreck stopped making the Whirlpool/Oreck XL 4000 series bags about five years ago. I guess there aren't enough of them still around to warrant producing bags. Your best bet would be to try and find a local vac shop in your area that may still have a pack lying around. I've seen people cut a wider opening in the newer style Oreck bag to accommodate the fill tube, problem with this is it will no longer have an airtight seal. I do still see them show up on eBay from time to time. Hope this helps.
- Karl