When I was looking into gravel syphons I found out that you can get different sizes of syphon for different sizes of tank. So, for instance, I have a 'small' syphon. It's got quite a big hoover-bit on the end, but it sucks up the water at a nice slow speed so I have more than enough time to give the gravel a good going over in my twenty gallon tank. It also has a gravel guard, but it didn't say it did on the decription (I got it off Amazon), so it may be that lots of them do have gravel guards it's just that they don't say they do.
Have a look on Amazon, or somwhere else that's sells a selection of them, and you'll see what I mean. The same type of syphon tend to come in small, medium and large. And you might only need the small one for your tank : )
Also my syphon only cost me six quid and it still does the job fine.
Hope that makes sense?