You don't say what size truck these rims are on.
So I will throw a few notes
Though I think here is nothing wrong with the split rims, I can understand tire shop skittishness over them.
I've never had trouble with them
If it is a 1.5 ton light/medium truck or less you should have no trouble finding later model truck rims that will fit.
I going to assume that your referring to your 1.5
You may want to contact a Heavy Truck dealer such as Freightliner, Mack, GMC etc or truck stop or heavy truck and equipment tire shop for tire replacement and/or for advisories of what and where to look for - They are usually equipped to handle split rims.
Try ALCOA
http://www.alcoa.com/alcoawheels/north_america/en/product_category.asp?cat_id=891 Here is just one website, though not in your local, that may be of some help in your research.
http://www.mutualwheel.com/parts/buyerguide.html A latter option.
If I am not mistaken Stockton Wheel can make you a custom set if your a absolute oddball with money to burn.
Also, should you change your rims, hang on to the originals and pass them to the new owner when you sell.