There's a seller on eBay that peddles straps for Parnis IWC homage watches, they should fit your Top Gun perfectly. No idea about quality though.
http://www.ebay.com/itm/22mm-black-fabric-Leather-Strap-Band-PILOT-fit-parnis-I-W-C-top-gun-series-044-/321033712420?pt=US_Watch_Bands&hash=item4abf19b324
http://www.ebay.com/itm/22mm-black-fabric-Leather-Strap-Band-PILOT-fit-parnis-I-W-C-top-gun-series-051-/221200550543?pt=US_Watch_Bands&hash=item3380948a8f
http://www.ebay.com/itm/22mm-black-fabric-Leather-deployment-buckle-Strap-fit-parnis-mens-watch-TT-044-/320985745138?pt=US_Watch_Bands&hash=item4abc3dc6f2