A pocket full of electronics, some bravery, and away you go. Do it yourself MSX projects are go with Frenchman Fabrice who has a list full of them. Some even for sale, in small batches.
In a world of modern hardware, making old clocks tick is a crusade only of the brave. Having an MSX computer, a system that was invented about 40 years ago, isn't something without worries too. She not only needs attention and a dose of love to keep running, no sir. Every now and then she needs a pair of new hardware. Keeping the precious happy is a priority before the poor MSX will leave you cold and withering during winter. Luckily, brave guys like Fabrice -aka FabF - can help out with that.
To witness FabF his running projects, just hop over to his website. Plenty of MSX hardware experiments going on there. You can find expanders, new MSX system, cartridges, adapters, expanders and current running projects like MSX4all and MSX_JAMMA.
The MSX4all project was originally a low-cost MSX DIY console. The FPGA used being quite powerful, the project has drifted to a more complete MSX with a keyboard and 64KB memory expansion. The final goal of the project is to respond to problems related to retro gaming on MSX and allow everyone to discover and play the entire MSX cartridge library in the best conditions.
The MSX_Jamma is an MSX slot for JAMMA machine. JAMMA stands for Japan Amusement Machine and Marketing Association who in 1985 created the JAMMA wiring standard. This allowed all Arcade Cabinets that were wired in the JAMMA standard to run any game built to this standard. So, MSX included with this hardware extension.
Other xo-hardware like the Neo-Geo Adapter, allowing you to use NEO GEO pads and sticks on MSX, Octo+, a self made MSX2+ computer, or the barbaric named 512kbmsxramsccsd card offering 512Kb RAM as a pseudo-ROM to load games into different mappers with SCC and SD storage. All good stuff to keep your 8-bit friend happy.
Fabrice will sometimes sell a small batch of his product, like the Expander 4K. A slot expander with gold contacts, activity LEDs, and low power consumption. He's currently offering a few boards for €75 ex. shipping.
With a growing number of hardware wizards like FabF on the MSX market, your MSX shouldn't be lonely too often. Plenty of hardware to go around, be it DIY or not. Not bad for an obsolete system from yesteryear.
relevant link: FabF hardware projects