That's where I got both. The themes that come with the manager mostly don't work and I can't find any recent themes for it. The one I'm using now is an old Conky theme. The number one theme on the first list I found on Google is 13 yrs old and #2 is 12 yrs old. It doesn't get better as you go down the list which came out last year. Surely someone somewhere is making themes for it and I just haven't found them.
Try DeviantArt.
Also @Tink on here has made some amazing Conky.
An important point to remember:
Conky is a scaffold that must be tailored to your hardware and specs.
So, for example, the network read may be off if you do not change the I.D. in your conky object to match your actual network ID
I make my own conky themes and I think most people do... So that may be why you are struggling to find themes.