For just the mixing, you could use any old gallon jug or pitcher (actual capacity isn't terribly critical and it needn't even be marked as long as it'll hold about a gallon), then divide the result equally into five one liter bottles and make up all to the same (full liter) volume -- then ideally squeeze all the air out of each before tightening the cap. An actual one liter graduate would be helpful for the making up step, but dividing equally can be done by eye if the bottles are all the same (say, one liter beverage bottles, which I buy with store brand club soda in them for 69 cents).
I use a collapsible (for easy storage) silicone funnel that I bought for the purpose for filling smaller bottles and returning chemicals to the storage bottle, but any plastic funnel will work fine -- just mark it for darkroom use only so it doesn't get used to fill up the Koolaid jug in the fridge.