Here's a superb, engineering-quality, siphon pump with a firm rubber bulb and an internal valve.

Inlet and outlet are machined aluminium, 10mm diameter barbed hosetails.

Flow direction is clearly marked with an arrow on the bulb.

Overall length 150mm.

Bulb diameter 44mm.

Weight 75gms. 

PROFESSIONAL SIPHON PUMP FOR 10mm HOSE #PROSIPHON2