How can I log simulated instrument time and approaches in a single-place aircraft?
Unfortunately, the only way for you to get simulated instrument time will be to rent a dual-control aircraft, or to use an approved simulator. Since you can do back-to-back approaches in a simulator, you may be able to find one that charges almost as little as the equivalent amount of fuel in your Long EZ. Especially since you can forego, startup, run-up, taxi, takeoff, landing, and shutdown.
The alternative to the above is to plan on dropping everything whenever you have a suitable IFR day, and go flying. Surely, there are a couple of IFR days in which the weather is not too severe every six months.
If you can deal with the fact that your flight time will not be within your control, you could partner with another aircraft owner of a two pilot place aircraft. That pilot will need a safety pilot as well. Then, you can just alternate who is under the hood.
Another, less convenient and effective, but more productive option is to schedule and budget a regular flight and ground lesson with a CFII once a year. If you make this a recurring lesson with the same career instructor, you can coordinate with them to make this a combination IPC/BFR. This and the random IFR day you may get in a years time should keep you current. It also has the additional advantage of possibly learning something new or relearning something forgotten.
All of the above options address the issue of staying current. None of them address the issue of staying proficient in your aircraft with your avionics. For this I suggest making half of our VMC approaches as actual or practice IFR approaches. You may not get the visceral experience of being in IMC. But, it will allow you to practice your proficiency.