Looking for a cheap option for the Generation III Gun in a month as I recently heard there is a stage with almost 40 shotgun rounds... So I think I will need a vest or something to hold my shells. Any advice?

re: cheap... I built a chest rig with a piece of stiff SCUBA webbing and suspended it from an Uncle Mikes LEO suspenders... attached  6 round trays... tied down with a small clip to keep from pulling up when grabbing shells....I have some shoulder problems now, so everything is lower on the belt...

for a NC Tactical match in the 90's (Kyle Lamb has a devious mind) ... had 9 in the gun, 7 on the side saddle, 8 on a 3 Gun Gear arm band, and (3) 6 round trays for a 36 round jungle run... had a Blackhawk shotshell bag with an extra dozen on the belt just in case

$8 piece of 1/8" thick kydex cut to 3" x 12", $2 of nylon webbing from army surplus store, and maybe $3 worth of plastic buckles from Army surplus store or Hobby Lobby. Drill and attach whatever caddies you like, attach extra caddies to your belt.

I can currently hold 16 shells on my chest rig on Taccom's new version of the Deuling Deuces, another new version of the Deuling Deuces at belt level on a Tek-Lok, two 8-up Qualoads on TekLoks, Two older versions of the Deuling Deuces on Tek-Loks, two MME 4 shell weakhand caddies. If i take my holster and mag pouches for pistol and rifle off, I can easily carry 64 shells on me, not including the 9 in the gun plus two match savers. Before losing weight I could have probably fit that all on my belt WITH the holster and mag pouches.