I have always had good experiences with Wranlger Power Products
. The link is to a 200 amp max, 105 amp idle output alternator with brackets for use on a '95 Defender. A little pricey, but a nice quality upgrade.
There is of course Mean Green
as well. It is a little disturbing to me that they don't actually put output numbers on their website, and I have heard both good and bad in the past about their products (starter's primarily), but another option none-the-less.
I had a 160 Amp Wrangler Power Products alternator years ago on a Pathfinder. It ran flawlessly for the 7+ years I had it, and put out about 95 amps at idle (measured by my mechanic at the time). As an Off-Road enthusiasts, idle and just off idle output was the most important to me...
Which ever way you go, don't forget to upgrade your charge and ground cables! (1/0 fine strand welding cable would be my recommendation). If you measure them out you can have Wrangler make them custom length for you. Again, very high quality materials, but not the cheapest game in town.