You need to obtain a license agreement from the Vikings, or the NFL which might have a centralized licensing process for all of the NFL teams.
You should also have a lawyer to guide you through this potentially complicated process & to possibly negotiate terms of the license if the Vikings/NFL are willing to negotiate their terms.
Alex Butterman is a trademark attorney with Staas & Halsey LLP (http://www.staasandhalsey.com), a Washington, D.C. IP boutique law firm. Alex is admitted to the bars of Washington, D.C., New York and New Jersey but, unless otherwise specified, the answer is intended to be general enough to apply to any U.S. state and based primarily upon his knowledge and experience with applicable federal laws. The opinions expressed are those of the author and do not necessarily reflect the views of his firm, Avvo or other attorneys. This answer is for general information purposes only and is not intended to be and should not be taken as legal advice. No attorney-client relationship or obligations are established herein, although consulting an attorney to discuss your specific situation is strongly recommended. This is especially true of trademark law because TM law is so fact-specific and full of esoteric nuances and exceptions that could easily result in a critical legal error without proper advice from experienced trademark counsel.
You have to get permission from NFL Licensing to do that, and the minimums are very large. Unless you will have six figure sales volume you are not going to make the minimums. There are no compulsory licenses so the NFL is very likely to turn you down. your only hope is to get an attorney who can approach them on a professional level. the NFL is seldom interested in dealing with amateurs. They are a professional league and they want to deal with professionals and only license to large volume manufacturers, distributors, and sellers.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.
Your best and perhaps only hope is to approach a company that already has a license from the NFL and try to enter an agreement with them to supply them with your etchings.