In keeping with what was said in the opening post: Since you aren't expecting to be riding at night I purpose that you get something that might be a bit brighter for added daytime visibility. I would suggest something like the DiNotte quad red. It won't run on AA's but the charge should last for days if you only use for two-three hours at a time on flash.

Most people on tours are still going to need to carry a phone and to charge it. If you stop for a hour or so you should be able to get at least a boost charge for your phone and the rear light if you carry along a small plug-in USB charger with multiple outlets. Of course if you are dead-set on something with AA's the DiNotte 140R with Red LED that uses AA's would be a good choice if you can find one. Otherwise you could buy something like the DiNotte 300R ( if they still sell those ) and build an AA battery holder to power it.

Lastly, you can buy an AA ( USB ) re-charger for your phone ( or USB rear light if you have one ). I've never used one of those myself but they should work although I'm sure it would take perhaps 8 AA's to recharge a phone. Doesn't matter though, AA's are pretty cheap and can be bought almost anywhere.