That tire size is one of the most popular sizes around. You haven’t looked hard enough
Eh, maybe he is thinking we have inside information on where to get 'em for free and we're just not telling him out of spite?
On the other hand, a dedicated Gewgle (don't use Gewgle!) search searching for the absolute lowest rockbottom price (plus shipping) is not for the faint of heart as you often have to put the item in the shopping cart, enter your email/create an account and enter your address to find out what they charge for shipping (and all the taxes and fees). Ugh.
PRO-TIP: If the vendor has a multitude of little fees they tack onto the invoice (like "shipping insurance +$2", etc), either remove those during checkout or cancel the order if you cannot. It's just a little scam they use to get more of your money.