I am looking for cheap fpv googles for my P4P+. Somebody of you have some suggestions?

Define your idea of "cheap".

A set of Headplay goggles run about $269.  Last time I looked there were 3 different versions of Fatshark from $150 to $350.  

I have both Fatshark and Headplay and the difference blew me away.  The main frustration was it is not ready for use right out of the box.  I had to buy the HDMI module for the Remote control, cables with mini-HDMI connectors at both ends (had to settle for mini-HDMI plus HDMI with an adapter) and finally, since I fall into the over 35 category, the two fresnel lenses that come with the Headplay do not let my aging eyes focus on the display so I also had to get an additional set of adapter lenses (RHO-Lens)

$269.99        Headplay HD 5.8GHz FPV Goggles with HDMI input
$ 98.00        DJI Phantom 3 HDMI Output Module (Pro/Adv)
$   6.99        Cable Matters 2 Pack, Gold Plated Mini HDMI to HDMI Male to Female Adapter
$   4.85        Gold Plated HDMI to HDMI Mini cable, 1.83 meters, 6 feet
$ 49.00        RHO-Lens High-Tech Optics for the HeadPlay HD FPV goggle
$428.83        TOTAL (not counting shipping!)

There are plenty of reviews on YouTube for both the Dominator, Headplay and numerous other models.  Just search for "fpv goggles comparison"

Sheesh, jump on to Amazon or ebay and search "FPV goggles for quadcopters" I saw a set for as little as $81 (and they probably perform like a pair of cheap googles!)

The absolute cheapest way is to get a set of something like VRBox goggles that cost about 25.00.  You put your device inside them and have a great picture with no extra cost. As far as the vr experience goes, I prefer them to my FatShark Dominator v3 goggles every time.  Added bonus, you control gimbal tilt by tilting your head with thr VRBox goggles.

The P4P+ has the built in tablet, and an external tablet or phone cannot be connected usingh the USB port, so solutions like LItchi and the VR BOX cannot be used with this drone.

Ref the Headplay, you need only the googles and the HDMI cable, as the P4P+ has the built in hdmi port.

I was asking for different models of googles with HDMI port

I use a Walkera Goggle 3 (Phantom 4 with HDMI module) and works perfect without interferences and best quality of images, but they do not cheap because in Italy costs 600 euro.