It looks like Natchez Shooters Supply www.natchezss.com
might have some of what you want left. These don't specify that they are boat tails so I'm assuming they are flat base. Is this the correct product number?
Product Number: BX33882
Product Title: BX 338CAL .338 200GR XSPIT 50/BX
Item Price: $34.70
Multiple Qty Discounts: 10 items at $32.99 each
Availability: In Stock
Shipping Weight: 1.72 lbs.