Offensive focused ward-items
We all hear that the support is who should be buying ward items, and I'm not disagreeing.
The items available in the game currently that offer additional ward charges
builds into 
are all generally best on champions who are playing the support role, with one exception
The 'support items' mentioned earlier all tend to focus around a champion's ability to sustain, and to help make up for gold discrepancies. Also, since vision is generally considered the support's 'responsibility' they get 4 charges from their completed items.
Tracker's Knife on the other hand is really just a strategic option, giving the jungler the ability to help with vision while still being able to invest in the stats needed to be effective in their role. As a result, Tracker's Knife offers 2 charges instead of 4.
Why can we not have similar options for other roles as well?
For example, why do we not have an AP efficient item that has 2, or even 1 additional charge of wards as an active option? Or one that is efficient for an ADC, or a Tank.
I will admit that there are actually a strange amount of ADCs who have abilities that improve their vision already, .. which is weird to me because there are not many supports with these kind of abilities. However, this would still be a good option available for those ADCs who do not have those abilities.
I would even like to see something like boots with a few charges.
What would this do?
This would actually two things as far as I can think of.
First of all, the support can still be 'mostly' responsible for securing vision, I'm not trying to change that. Having viable options available for other roles will not only relieve some of the burden from the support, but it would also help to remove some of the dependence on the support for providing vision. I'm sure that everyone has had a support who fails to ward effectively and purchasing one of the existing items for yourself is simply not cost effective so you are simply forced to play with the minimum vision available.
The other thing that this could potentially do is to give the support more options for items to get their vision from. As I mentioned before, my theory for these items would be to increase offensive stats, and decrease charges. These items would also very likely be more expensive, so this may not be as common of an option, however if the team is doing well enough on vision and additional damage could be helpful to close out the game, they would now have this option.
I don't expect that everyone will like this idea, but at this point that is all that it is.
I haven't really put together any solid ideas for what kind of items would offer this and I imagine that there would most likely be some compromises available to make something like this feasible.
As suggested earlier, the number of charges could be on the table, or maybe the type of trinket placed. For example, maybe an ADC vision-item could give them 1 charge of a blue trinket every time they base. This way they can place the ward from a greater distance for safety, but it is visible and weaker.