Simulators
FireMobileSimulator - Firefox plugin for Japanese Mobile Web Development. Simulator with handset sizes, user agents, emoji, etc
A 3rd party simulator - Supports 500 handsets, including docomo, au and SoftBank. Yearly licensing (55,000 ~ 85,000 yen) seems a bit costly.
i-JADE Basic is an iappli emulator for P504i.
Others
Inspect the headers of your mobile phone by visiting http://www.mobalean.com/tools/headers, or use this QRcode:
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Here is another for docomo, with the guid=ON to reveal your i-modeID
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