Depending on how heavy your usage is, you can probably get by with the ANA *alliance award search tool and setting your UA account to expert mode. The details are in the UA forum. Basically, by setting it to expert mode, you can see the fare bucket availability for all UA flights (for paid seats, award seats, and upgrades).

That said, I ended up getting an expertflyer subscription, initially because I needed to check LX award availability. (The ANA tool does not include LX flights). I found that I really liked the ease of use and the functionality, and the ability to set alerts for the release of award seat availability is extremely convenient. It isn't that expensive so I ended up keeping the subscription.