dom pretty much hit it on the head - there is nothing special about a flooded lead acid battery, as this is the most common automotive batteries, including the ones in your Toyotas are the flooded type. These can be both maintenance free and maintenance type batteries. If the case is transparent or not is not important or an indication of purpose.

Some owners prefer AGM (Absorbent Glass Mat), drycell, gel type batteries, or exotics like LiPo and LiFePO4 - really depends on what you want to spend and what your requirements (ambient temperatures, frequency of driving, temperature extremes, etc.) are.

There are pros and cons with each type - up to you to find out which fits your needs the best. I've run flooded, gel, AGM, and dry cell batteries - none really stands above the rest, in terms of able to start the car and provide a reasonable amount of reserve power.

When its time to replace the battery - pick one that fits your budget, has the appropriate group number (physical size of the battery and terminal type), has atleast the same or more CCA than the battery it will replace, and warranty that you will be happiest with (some are prorated, some have replacement clauses).

Sounds like a plan - as mentioned by dom - most OEM group 35 batteries are in the 400-450CCA range, but you can find lots of aftermarket group 35 that are in the 500-550CCA+ range. Interstate is well known brand - made by Johnson Control. Huge battery company, they make or have a large part of the manufacturing of these brands and OEMs (as far as I know):

dom already got you that information - group 35 would be the closest fit.

Reason you are likely having a hard time find the exact battery size is that the Subaru part number is following the JIS specs (Japanese Industrial Standard) while cars sold here follow the BCI specs (Battery Council International). Same basic battery, just two measurement/sizing standards. The thing to keep in mind is the "size" of the battery posts. Not sure if it is still the case, but older JIS specs had posts that were smaller than the SAE posts. Should not be an issue with import cars, as they use a different style of terminal clamp, can tighten down further than older solid lead clamps designed for a conical shaped SAE post.

Here is some common cross-references for JIS-to-BCI conversions from a quick web search: http://www.chadspictures.com/automotive/How-To-Change-Replace-Toyota-4Runner-Battery/Toyota-Battery-JIS-To-BCI-Cross-Reference-Chart.html

Might try the forester forums - lots of people are asking the exact same question as you are. http://www.subaruforester.org/vbulletin/f85/2012-forester-oe-battery-n-models-110695/

From the description - 65D23L is a JIS size 23L, the number 65 "supposed" to indicate the Ah rating (steady state transfer). But many on the Forester forums are seeing 48 Ah to 52 Ah as the apparent power (equivalent to a 400-450CCA sized battery)