Probably a little late to say this, seeing as I just found this post, but I got all of my sunstones from transmuting. First, went to Avery Templeton (CL base camp, TC vendor) and bought transmute sandstone (10 stone blocks) and transmute Sunstone (15 sandstone) . Then, I went to my main farming place for stone blocks and raw sandstone: stone town in ZF. There, I got all of my needed stoneblocks=sandstone=sunstone. Hope this helps if it's not too late!