You could get by with the lighter duty 48 or 60 inch Markham that cost significantly less. I use a 48 inch
grapple (Millonzi...similar construction to the Markham) on my Kioti DK40se with a 2700lb lift capacity at pivot pins which is pretty close to the LA1002 in terms of power. My 280lb
grapple has taken all sorts of abuse and works fine. The Markham 48 is a slightly heavier build and would I am quite sure meet your needs. Don't make the mistake of thinking that you need a
grapple as wide as your primary bucket.
With a M class Kubota you must already have some rear remotes. You could control the
grapple then simply by running a couple of long hydraulic hoses with appropriate fittings from the rear of the tractor to the
grapple. Cost from an internet hydraulic discounter would be about $100, from a dealer maybe $200. Lots of people (including myself) have done this and are perfectly content. If you decide later to upgrade to a diverter valve or electric over hydraulic valve you can recycle the hose and fittings so there is almost no disadvantage to trying the rear remote first. The only practical thing you need is a rear remote controler that is conveniently located for you to reach with your right hand.