Hello Adil, Its very hard to find Suzuki Parts in Market Specially Tank and side covers. I already have this experience as i have to GS-150 and i search a lot in Rwp / ISB area at the end i found these things from Lahore on OLX and asking price was so high.
The best option is first wrap your original parts with good Plastic Coating and then Paint it or design it with Sticker mostly used Carbon Fiber look stickers. Also some people do a leather wrap on there GS-150 which look good.
If you have any other questions regarding to GS-150 you may ask. Thanks