Does a tennis racquet bike bag exist?

[KatyMac]

Ideally not a rucksack, but pannier bags or something?

Not something I’ve ever seen

Me neither

you can get pannier racks for sports (see it mostly for surfing) that can take large bags and equipment.

As above - a pannier that lets the handle stick out. Most will work and they are plenty of cheap ones around as well as fancy brands

You can get panniers that are wire baskets, which you could put the tennis racket in its case in.

Sports panniers, I'll have a google

I live in an area where it is normal to cycle everywhere - usually people just put their tennis racquet in their normal pannier, with the handle sticking out. Ortlieb are the best, they are built to last and you can buy spares readily. But any roll-top pannier would do, so that you can close the pannier on one side and have the handle sticking out the other side. Decathlon's offering is usually pretty good, and kinder on the wallet...

That's what dh does but I was just looking for something waterproof