Small Tank

If you get one of these cylinders along with a valve you should be able to fill your Mrod to 3000psi (shooting it down to 2000) over 3 times (3.8) if you start with 4500psi in the tank.

https://www.aliexpress.com/item/4500PSI-300BAR-High-Pressure-Compressed-Air-Carbon-Fiber-0-5Liter-500CC-PCP-Paintball-Tank/32756688151.html



I personally don't feel 100% safe using the chinese tanks yet, but there aren't any non-chinese tanks in this price range. It's a bit on the larger size but I would go with the 90ci Ninjas tank with regulated output of 3000psi. These tanks will give you 10 fills.

https://www.crosman.com/airguns/airgun-accessories/pcp-charging-system-15

or the Benjamin 90ci tank with jubilee valve.

https://www.sportsmansguide.com/product/index/benjamin-pcp-4500-psi-15-charging-system?a=1899952

Or using the AGN code you can get it from crosman on a Friday for $304 delivered.

https://www.crosman.com/airguns/airgun-accessories/pcp-charging-system-15



If these 90ci tanks are too big you could always put the valve from either of these tanks into a peanut paintball tank. You'd still get 6 fills with the peanut

https://www.amazon.com/Ninja-Carbon-Fiber-HPA-Tank/dp/B00BNWYFD2/ref=pd_day0_hl_200_1?_encoding=UTF8&pd_rd_i=B00BNWYFD2&pd_rd_r=d83f0bf2-db7f-11e8-940e-5b72383d914d&pd_rd_w=rnj4y&pd_rd_wg=LAAGn&pf_rd_i=desktop-dp-sims&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=9E07CG74PVK2TQHVVS3E&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=9E07CG74PVK2TQHVVS3E

Then put the paintball regulator into the 90ci tank and sell it to a paintballer to recoup some of your $$