There are other ways but none are very practical for your purposes. You can read an old blurb here on some other ways of determining ABV if you like ... it's pretty much sleep-time reading material tho.
Note my comments on using a vinometer there ... something that one otherwise might think to turn to ... but even the suspended colerant in red wine makes a vinometer inaccurate. I'd think peary is probably out.
Fresh pressed pear juice will run within a range of SG.
I did a quick google search and found one person stating that their fresh pressed pear juice had an SG of 1.065. This is a bit higher than most cider and apple juice I've seen which seems to run in the 1.040 to 1.050 range commonly ... though I'd expect that the juices would be somewhat similar. If pear juice's range is similar to apples, then the spread of 1.040 to 1.065 is useless in calculations as it is too broad a range.
You might specifically ask online to people who make Peary (hard pear cider) ... other than that ... guessing by taste is about the only other alternative.