It never helped when Trent Barton put their Zigzag Plus up to £10 at the beginning of the year, making it £1.10 more expensive than the Wayfarer.
Except the Derbyshire Wayfarer has also now gone up, to £10.50 (though the adult price includes one free dog or child, if you're so minded).
The Derbyshire Wayfarer ticket is widely sold at tourist info centres, many libraries and any bus travel centres in Derbyshire and some adjoining areas where it is valid (such as Sheffield, Burton and Leek). So if you know you might be returning within a couple of years, normally travel from outside the area and are prepared to spend the money in advance it's worth buying your next ticket while in the county (that would also avoid the price rise - I wish I'd bought a couple more at the old price earlier this year).
That usually saves me, when travelling from Birmingham, hopping off the train at Burton, dashing up the stairs and dashing back down with a Wayfarer to continue northwards about 10 mins later!!
Rail ticket offices and bus drivers print off the ticket on normal stock - it's only the 'wallets' they're likely to run out of, but the ticket is still valid and at a push you could ask for an empty wallet on the next bus or at the next staffed station you alight at.
One reason to ensure you get the wallet or a scratch-off version is the freepost draw to win another ticket if you send back the details on how and where you used the ticket - yes, it's genuine: I won one last year.