Get a few kitss off of a $1 shop...those kits are usefull
Lost my ody top seal in the drain while cleaning it (brain fart) and it appeared that I had 3 nice orange ones as spares.
The kits usually have like 5 big enough to cover the tele and 5 for your garden hose as well
Must be like 50 o-rings in that kit for $1.25
Edit:
...and I use 1 thin 0.75'' to seal the space between the collector cup top cap of my GGTS and the ody to keep full air adjustment and stabilise the lot!