Missouri Meerschaum: Replacement Stem: Black Filtered Bent

I ordered stems for my Meershaum pipes a little while ago and paid 89 cents apiece. Great stems. I chew the ends off my stems, so one lasts me about a week. I need to order some more now but WOW, the price has increased to $1.98 apiece. I can't afford to pay that since I go through a lot of stems. Do you have any discounts for large volume orders?

Would it be possible to have specs of the outside diameter of the insert? My dad has an unbranded pipe and he really likes it but he broke the filter tip.