Decathlon sell a strap that will work with your 800 and it will even accept transponder from Garmin as press-stud spacing is the same.https://www.richersounds.com/panasonic-dmpbdt380.htmlAlso has Bluetooth should you wish to upload to whatever.Very happy with mine.
My Garmin strap is still going well after 5 years, I always unsnap the head unit from the strap after use so that the contacts always dry out
Kim, you are very bad!
I have an Ebay "CooSpo" chest monitor. It's fine but looking worn after 2 years. £18 so I don't mind replacing every few years.