As a large language model, I cannot access and process real-time data. However, I can guide you towards resources where you can find data relevant to your MPhil research on the vegetable marketing system in Dhaka, Bangladesh.

Here's a breakdown of data sources categorized by your research areas:

1. System Structure and Performance:

• Government Agencies:
  • Bangladesh Bureau of Statistics (BBS): Annual Survey on Crop Production, Statistical Yearbook of Bangladesh. (https://bbs.gov.bd/)
  • Department of Agriculture Marketing (DoAM): Reports on market structure and performance. (Check their website: https://dam.portal.gov.bd/sites/default/files/files/dam.portal.gov.bd/page/5874b31d_fcda_4bd8_98bd_9b127a20a9a8/2021-11-04-04-55-c32d2033d52c923e488575f62671a52b.pdf)

2. Efficiency and Sustainability:

• Academic Research Papers: Search databases like JSTOR or Google Scholar using keywords like "vegetable marketing system," "Dhaka," "efficiency," "sustainability," "post-harvest losses."
• World Bank Open Data: Data on agricultural production and environmental indicators related to Bangladesh. (https://data.worldbank.org/)
• Food and Agriculture Organization (FAO): Data on agricultural production and food security in Bangladesh. (https://www.fao.org/home/en)

3. Comparative Analysis:

• Government Reports from other cities: Look for reports on vegetable marketing systems in cities you're comparing with Dhaka.
• Research Papers: Search for academic literature on vegetable marketing systems in other South Asian or Southeast Asian cities.

Additional Tips:

• Contact relevant government agencies directly: They might have unpublished data or reports that could be helpful.
• Consider conducting field research: Surveys of farmers, Beparis, Aratdars, and retailers can provide valuable firsthand data.
• Search in Bengali: Government websites and research might be available in Bengali. Use keywords like "শাকসব্জী উৎপাদন" (Shak-shabji Utpadan - Vegetable Production) and "বাজার মূল্য" (Bazar Muljo - Market Price).

Remember, data availability can vary, so check publication dates and data collection periods to ensure relevance for your research.