Use a AC plugged device with a battery
It depends on the run time you want.

An AA alkaline battery has about 2500 mAh capacity. At 450mA, the batteries would be depleted in about 2500/450 = 5.5 hours.

D alkaline batteries are 12 ~ 18 Ah, and would last between 26 and 40 hours run time. This is probably more cost-effective than running AA's.


Have more of a budget and want a longer run time? Get a car adapter for the Roland and use a 12V-type car battery.

Adapter: https://www.directnine.fr/products/myvolts-9v-incar-power-supply-adaptor-compatible-with-roland-td15-drum-module

A 'Group 35' auto battery (typical small car): about 50Ah, which stepped down to 9V is abut 77 Ah. Run time would be about 111 hours.