Are you sure it's 1998 or in your case ST1100AW should be on the frame under the seat. 1998 ABS is black and we didn't get blue (Midi Blue Metallic) ABS until 1999 or 1100AX (mine). There was a blue back in 1995 (Atlantis Blue Pearl) or 1100AS which was the first generation ABS/TCS and no CBS (Combined Brakes)
Any case if you can't find local you can buy new from the UK
Cover 65 UK pounds or about $AUD110, mirror same on all models and same price as cover so about $220 plus postage.
Australian price (depending on dealer) about $380 for the LH side.
I can get part numbers But I need the right model first.