Is there an alternative to the T61p 6 or 9 cell battery?

I'm thinking of course, something like a battery blank. I know something of the sort was available for my old dell, simply a plastic place holder, it would allow you to run without the battery, but still have something in that spot to prevent dust, damage, reduced case integrity, or other problems. I've looked around pretty extensively, but haven't managed to find anything of the sort. Thoughts? I'd be able to use the batteries for travel that way, but 90% of the time I'm on AC power, and would really like to be able to run without it (yes, I know, if the power shuts off you lose data, ).

Alternatively, anyone know if there are manufacturers/resellers that do the same battery size etc? I have a 9 cell now, which works fine, but I would prefer the smaller 6 cell (its the 15.4 inch model), for both weight, and to not have it protrude from the back. However, I really don't have any desire to spend the absurd amount for a replacement 6 cell directly from lenovo (assuming I'd ever get it to begin with).

Lastly, I haven't looked into this extensively, but I gather the battery type for the t61/t61p's are the same line as the t60/t60p etc? I'm just curious, I find a lot of websites don't even offer t61p as an option to select when searching for accessories. I find that a little odd, given that its been around for a fair while now.