If you can find the code for the insert, it will help. You can search for the insert code, and probably pick up a lot of sources and manufacturers. If you succeed, you would be safest buying from a supplier based in your country, should any problems arise.
Warco do not appear to sell anything similar.
Take a look at Arc Euro Trade site. They sell GTN inserts in 2.2 and 3 mm widths, which might be suitable.
Their MGMN inserts are double ended and are either TiN or AlTiN coated, but only come in 2 mm widths. They might be too long for your holder. (These are used in the MGEH holders )
HTH
Howard.