The Blu is a super mini and is pretty nifty looking PV, however the company has had some problems and from
reviews here on ECF you'd be better off to purchase from another company.
The Blu is made by Shenzhen Jiashibao Technology Co. and is a model L88B Specifications: 88mm long, 8.5mm dia, 10g weight. 60-80 puffs per cart (well, that's what they say... LOL!),
90 mAh battery.
A good similar model to Blu would be the Volcano L88B which also has a PCC and is the same thing. That said...
If I were to suggest one thing is that you shouldn't be concerned so much with the size being identical to a cigarette. The smaller the e-cig, the shorter the battery life. The mAh rating will tell you how long the battery will last. The smaller the number, the shorter the run time (see underline above).
Also it is more difficult to find replacement parts for the models similar to Blu. Because they are scarce they are usually high priced.
The 510 (112mm long, 180 mAh battery) and 401 (107mm long., 180 mAh) models are similar in size work very well (I have used both) and both have a PCC case option and passthroughs available for purchase also that will work with them.
I'd suggest you go with either of these instead as they are dependable, have long lasting atomizers and most suppliers will carry the 510 or 401 model parts, so purchasing the replacement atomizers will be easy and relatively inexpensive. If you decide to transition over to a battery modification (Mod) unit, you'll be able to do so with the atomizers you already have from either of these models. Adapters are made to fit these as well so you can use other model batteries or atomizer models for the 510 or 401.
If you decide you want more battery time, but don't want a battery modification unit you can purchase the larger mAh rated stock batteries (Mega 208 mAh which are longer and last about 4 hours) for the 510 model later or go with the Ego (Janty) or Tornado (TotallyWicked) unit for the 510. These are rated at 650 mAh (about 6 hours of use). A similar clone (Hello 016) unit has 1300 mAh.
Last tip is what ever you decide to purchase, get a kit with Manual button batteries rather than autos. Automatics can get liquid down inside of them (air hole for activation when you take a drag is open at the battery end) and will have a shorter life. If you decide to drip, it can cause problems with the autos.
*Edit* Kent gave you a good option as well with the Joye 306 super mini. Another good choice! I forgot about that.

From what I can find, it appears the 306 is 96mm or 98mm in length and the battery is 150 mAh.
I didn't see any other option but automatic for the battery for the 306 though. I'm also not sure if it will fit in a 510 PCC to charge. The information says they are 510 compatible, but not with the cartridges or the 510 PCC. I think some get around this by putting a cartridge top on the end of the battery to lengthen it to charge in a 510 PCC.
Happy Vaping!
