Hi,
I bought a Eulit open mesh NOS perlon strap on eBay from a dealer in Australia. AFAIR they are West German 1970s, about £7 plus postage. Mine was pale grey but they also do maroon both of which should look good on an Everest (well the grey did on mine.) Has a nylon/perlon keeper and a better buckle than most of the perlon straps I've tried before.
G