Ebay for a 2nd hand CAAD8 (or CAAD anything, mines a CAAD4 and still in regular use as I’ve not been tempted off it!)
TDF starts next month though so get in early as next month the world and his dog will be buying a road bike so everything on sale now will be back to RRP and ebay prices go mental, last year I watched a CAAD10 go for above what they were selling for in the shops rather than the ~half price they get sold again for in September when the wanabee MAMILS give up!
This years great for buying cheep bikes as Ultegras being superceeded by 11 speed next year so there’ll be lots of cheep upgrades floating about when that’s released. And while there’ll be a lot more to the new groupset than an extra cog, the outgoing stuff will last another 10 years of sunday club runs at least.