Casio STL-S100H-2A2VEF Tough Solar Watch With Blue Resin Band - USD $18.23 plus $5.89 delivery.
A nice feature in the top left of the display there are 3 charge bars to show the amount of charge.
This one isn't solar but if you are after black then it's a similar price -
Casio W735H-1AVCF Super Illuminator Black USD $20.99 plus delivery (approx AU$35.00 delivered)
More Casio watches here in the "Up to 20% Off Sale"
Edit - For those that missed out this is the cheapest Casio Solar I can find.
Casio W-S220-8AVCF Grey US$19.88 plus delivery (approx AU$34.00 delivered)
Camel price check.
Other Casio Posts
Genuine Classic Casio Watch: Resin Strap $12, Stainless Steel Strap $25, Illuminator Stainless Steel $25 etc - Posted @ Amazon
Genuine Casio Watch: Data Bank $40 or SS $47, Tough Solar $48, Casio Royale SS $39 & Samsung Gear S2 R720 $280 - Posted @ Amazon
Casio Diver MDV106-1AV USD $48.07 Delivered (Approx AUD $63.50) @ Amazon
Awesome price for a solar powered watch! :) Also, this watch looks good too with a 10 year battery?