Your local parts stores have them, they're just being lazy. It won't be listed as a "longer travel" shock for a Samurai - you just need to ask them to crack open the books and get ones that are longer than what you have (measure it eye to eye collapsed and extended all the way). Is it 2" total, or 2" up 2" down (total of 4") longer? Whatever it is, give yourself another inch as "room for error". Get the cheapest shocks they carry - like the $10.00 - $15.00 ones. The cheaper they are, the softer they are - which is exactly what you need in a vehicle that weighs less than a gallon of milk.
The BEST way to do it is to flex your suspension all the way down (take measurement to your shock mounts), and all the way up (take measurements to your shock mounts again), give yourself an inch for room for error, and have the parts stores crack open the books. If I remember correctly, stock shocks can handle Calmini's SR just fine though... they didn't recommend changing shocks when I inquired. But, I'd bet you SHOULD change them - they're probably old and over-due to be swapped out.