Hello & Welcome to Just Answer,
Sorry I didn't see your question earlier.
I just did a comparison of the 3 least expensive HANDHELD Garmin devices, and it looks like ALL of them have the ability to calculate the area of the paddock (or any other area walked around). I have a screen capture (attached) of this comparison, along with the list of features for each device and the current "list price" of these devices. It appears the eTrex 10 is the least expensive, but you MAY want to look at the other features listed - in case one of those features might come in handy in the future.
I also have a link to a video that shows how the Area Calculation works on these units. NOTE: The video shows a different model, but the process is the same on most Garmin units.
Click here for video --> https://www.youtube.com/watch?v=-MXnAmMfRvc
I hope this helps. Please let me know what you find or if you have any more questions.
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Thanks, ***** *****