I am looking for a shakeyhead that weighs 5/16 oz. with a 3/0 EWG hook. Any ideas? I know I can get a 3/8 oz. size but would really prefer the 5/16.

size with the 3/0 hook.

Try e bay, I believe there are a few guys who will make custom shakey heads to specification. 

A lot of them on ebay, that's where I got mine.

If you can get by with a 1/4oz these:

 

https://www.tacklewarehouse.com/Big_Bite_Baits_Shorty_Gamakatsu_EWG_Head_4pk/descpage-BBBSHH.html

3/0 Gammy hook too

6th Sense Divine Shakey Heads 5/16 oz with a 4/0 hook

Try these in 1/4 I've weighed them myself(1/8-1/4) on my scale and their shaky heads always weighed heavier than advertised.   https://www.tacklewarehouse.com/Megastrike_Shake2_EWG_Pro_Model_Shakey_Heads_4pk/descpage-MEGAEWG.html

51 minutes ago, Wprich said:

Try these in 1/4 I've weighed them myself(1/8-1/4) on my scale and their shaky heads always weighed heavier than advertised.

A lot heavier or a little heavier?

 

Remember that any jig-head lure (swim jigs, chatterbaits, spinnerbaits, etc) will weigh more than what's stated on the package. The stated weight is JUST for the head...you have to add the weight of the hook(s), plastic holder, skirts, blades, etc. to get it's 'true' weight.

Try Siebert Outdoors, and see if Mike can make them.

 

https://www.siebertoutdoors.com/

16 minutes ago, MN Fisher said:

A lot heavier or a little heavier?

 

Remember that any jig-head lure (swim jigs, chatterbaits, spinnerbaits, etc) will weigh more than what's stated on the package. The stated weight is JUST for the head...you have to add the weight of the hook(s), plastic holder, skirts, blades, etc. to get it's 'true' weight.

Yeah I know what's on the package is just for the head of the bait and not the total bait.  The total weight is just enough that the 3/16 weighs about 1/4 and the 1/4 weighs about 5/16 in my experience with them.  I figure the screw lock, hook, and the glob of paint they put on them is what pushes the total weight up.