I know you don't want to, but use a combined table. If there are specific differences that are supplier specific, you can use related tables that are supplier specific for those details, but keep a unified table for all the fields that are common to all the suppliers.
the 4 Supplier tables are potentially going to be changing regularly and at different times.
I really don't see why that requires separate tables. You can work with groups of records specific to a given supplier without having to keep them in separate tables in order to do so.