Can I look at and select to buy online if I don’t make the purchase until after Tisha B’Av?
It is permitted since you are not actually buying it. However, according to some authorities it isn’t correct to go window shopping for things that may not be bought during the nine days during the nine days, which would include online window shopping.
Poskim Mikdash Yisroel 69, The three weeks pg. 67.