Daiwa makes a reel similar in size. Think its 900h?
Nice reels to do bottom fishing with. I have a red senator 9/0. Still is my grouper work horse. No idea about drag upgrades, but I could use some if there are any.
You can contact smoothdrag and see if they have some to fit the 9/0. They list 10/0 and up and 6/0 and smaller, but I don't see 9/0. They are good people to deal with.
Also, if you have an older Senator with the old style rubber drags (or really old with leather) you definitely should upgrade to the HT-100 drags and new metal drag washers. These drags can pull anchor when buttoned down.
You will notice a huge difference over original drags with the Ht-100s
You can get over 30# of smooooth drag out of greased carbon tex washers and 28+ out of the HT100's from both the 9/0 and 900h I have both reels both have over 900 yds of 80# on them I'm sure I could get close to that with 100# braid Great reels for a wire set-up for Hoo or inexpensive reels to fill your spread that will last a long time the 900H I have is about 1990 vintage still a beast I cannot bring myself to sell it or the 9/0 They work why waste the money You never get what they are worth in the used market
The stock 9/0 is a great reel. Tough but not bullet proof. Newer Aluminum spool corrodes rather easily. The older bronze spool lasts forever but the plating peels off. If newer it comes with the ht100's already. Just remove and grease them with Cal's or Shimano grease to waterproof them a bit... per Alan Tani. It works.
Refrain from running high lb test braid and over 100lb mono. High drag settings are not what it was meant for. Single dog will fail... trust me, my dad and I are guilty of it. That little bronze piece will either bend or break. Or if you do just run lighter drag and test it to keep it below 30lbs or so. I'm not too sure of what it does at almost complete lockdown... but I think I measured 28 or 30... but I could be wrong. And the dog still failed.... not once.. not twice... but until we retired the reel.
Most important is to keep the dog clean and lubricated to prevent stick. This contributed to a couple of sprained fingers burnt thumbs.