Maybe @ColT can sell you one of his steeds and we can call it a day. 
Your run ins with Merida and Giant are quite normal. They probably only keep a handful of frames above 56CM or 58CM for domestic sales since the average height is 10cm shorter than you.
I know that @okonomiyaki just bought a large frame Taokas Striker SL from Jester Bikes, but they said that it was the only one left and he got super super lucky. He didnât even get to see the color and he ordered it.
You may not be able to find a complete bike, but you could look into putting something together. I know that ROXYCLE, the bike that I ride, has large frames available. However, you just have no way of test riding or even seeing them in person. Just have to go by the ownerâs FB and the pics he posts. I can vouch that they are pretty damn good bikes and if you want credentials, ROXYCLE sponsors the no.1 Taiwan women, Huang Ting Yingâs track bike. If youâve seen her legs and her track races, you know the bike needs to be stiff AF for her not to brake in half.
I also know the owner of another small brand in which the frames are all made in Taiwan, but he mostly sells in US. PM me if you want details.
I had a friend who was about your height and ordered an unbranded black carbon frame from a Chinese factory and it cost him around 30,000NTD (including shipping fees) to put together.