I have always problem with keeping my thicker music books opened on music stand especially when they're new. They are stiff and closing by itself if not held so I thought maybe some giant clip would help? Anybody using something like that?

There are several products like these.

Interesting implement, BDB--- like a big, spring-loaded clothespin, made of chopsticks.

US$4.99 is not bad, but I have heard the ladies say that the clip used to hold hair on the curlers while it sets, works well and costs a fraction. It looks kind of like a crane's bill.

You might have to know a girl to get one.

I just use the wide clips bought in grocery stores that are designed to clip potato chip bags shut - works fine.

Bulldog clips. Varying sizes. You can flip `e, over usually . . .

I always take new music books to the copy store and get them spiral bound. Wish publishers made them like that in the first place!

Spiral binding leaves the pages perforated, and they tear easily. Also, they take up a lot of space on the shelf.

I put a clip on each lower RH corner of the book, then wedge the clip behind the lip of the music desk so the book can't go anywhere.
This may be done in addition to using the clip at top center that looks like the letter m.
Seems to work like a charm.

I usually make copies of the piece I want to play. This way, I can also put 3 or 4 pages next to each other and don't have to turn pages.

Maybe in the future each piano will come with a tablet computer with score reader. But until then...

I have a couple of those clothespin/chopsticks hybrid clips and they're awesome. I used to use regular old fashioned wooden-clippy clothespins before that, but once I got the extended version, I never looked back. Another good quality of the fancy kind is they have a transparent front, so one can see the music through them if necessary.

Also helpful to make sheet music stay open is to do an old-fashioned "book opening", especially with perfect bound books of scores. Back in the day, they taught us how to do this in school, but today it seems to be a lost art.
Here's an illustration courtesy of AbeBooks
And here's another version

ETA: The book-opening thing works best if you do it first thing, before the book gets "trained" to want to open at one (or more) particular places.