There are tons (just search "vacuum cleaner adapter" on Google, Amazon etc and you'll see what I mean) but you need to know what you're trying to adapt to/from.
a 1 1/4" (32mm) male handle end is considered "industry standard" and therefore "industry standard" tools will have 1 1/4" ID.
Some tools (Hoover, Filter Queen, Royal) have a 1 1/4" OD and were made to fit inside the hose handle.
Miele vacuums use a 35mm connection (male handle, female tool). SEBO is slightly larger (37mm?). Many commercial vacs (backpacks especially) use a 1 1/2" ID hose cuff and 1 1/2" tools fit inside it.
Shop type vacuums traditionally used either 1 1/4" or 2 1/2" male hose ends, but there are now some that use an intermediate 1 7/8" size.
You may also have luck making your own adapters out of short pieces of vacuum wand, or hose cuffs, or even plumbing parts. I have done stuff like this but usually it doesn't end up fitting or working as well as a "ready made" adapter if you can get one.