if you only plan to play a few MSX 1 cartridge games, the US spec CX5M will do. Most likely you will need to make your own video cable as most eBay auctions I have seen come without one and it's not a standard cable (but rather easy to make one tho). Typically the going price for those nowadays is between $60 to $120 depending on the condition.
If you want to play MSX2 and up games (think Metal Gear, Vampire Killer), it's easy to find one on eBay, although they can be pricey. Japanese models are best for using in the US as by default they will boot in NTSC mode. European model can also be switched to NTSC but by default will boot in Pal.
Keep in mind that Japan use 100Volts vs 110 in the US so you will need something like this to keep it safe:
http://www.amazon.com/VCT-VT-1000J-Japanese-Transformer-Converts/dp/B000PC4SVU/ref=sr_1_1?ie=UTF8&qid=1415590847&sr=8-1&keywords=japanese+step+down+converter
I would also recommend a Megaflashrom SD which makes it easy to copy files back and forth from a PC using an Micro SD card. The latest model also has a 512KB Ram extension built in which can be useful as most Japanese MSX only come with 64KB