I "think" you're looking for a hydraulic fluid labeled as 'AW-140', which is commonly seen in specs for older units: note this is memory and I'm unsure of the 'AW' nomenclature. I don't know a thing about your particular machine, but NIW thinks it's an older unit and he's pretty knowledgeable.
In my area the -140 hydraulic fluid is rarely seen on the shelf (AW-46 is another example) and sometimes has to be ordered in. Any hydraulic fluid labeled as being -140 will meet your needs regardless of brand.
I tend to stay away from the 'Universal' type ('303' is an example) hydraulic oils as I think they're 'universal-type' for a reason: they do a lot of things marginally but do nothing well.
One thing you might want to consider if converting to a newer high-performance hydraulic fluid (example: Kubota's line), you may start finding new hydraulic leaks as the newer fluids sometimes find ways to get out that the old thicker fluids would ignore.
There's also an argument about mixing fluids. Most Forum members tend to stay with the same 'type' and brand. That said, I have a neighbor that goes around to dealers collecting their empty 5-gal buckets and drains out the few ounces in each can until he collects a gallon or so then adds it to his 1970 Case backhoe. It continues to run and leak and apparently doesn't care about mixed oils. That thing probably has some 10W-30 in it by now.
Please post back with your continuing experiences so we may all learn.