As for the components (\$\alpha F\$) in the question, I've checked the schematic, they are shown as R2 and R5 but no details have been given.
Most likely they are protection elements: could be a fuse or even a resettable (PTC) fuse (I'd prefer the latter, though, since the product is designed for 4-20mA.). They can even be from German company Alpha-Therm.
SMD resistors are perfectly acceptable for this purpose. You need to choose your resistors for both voltage and power rating. You also have the option to use more than two resistors like you have shown: the space occupied by having two resistors in series in each leg (4 resistors total) is still tiny compared to the through-hole resistors you used previously.
Be sure to size your resistors to handle possible over-voltage conditions. You can also specify resistors that are either fusible or flame-proof if required by your certifying authority.
Resistance is resistance; there is no difference between using a 68ohm TH resistor, a 68ohm SMD resistor, or a 68ohm carbonized strand of cotton, assuming resistance is the only criterion you care about. It isn't, but you've already handled power dissipation by specifying a certain amount and finding an appropriate SMD resistor.
Best Answer
The product in the photo is Gravity: Analog Current to Voltage Converter.
As for the components (\$\alpha F\$) in the question, I've checked the schematic, they are shown as R2 and R5 but no details have been given.
Most likely they are protection elements: could be a fuse or even a resettable (PTC) fuse (I'd prefer the latter, though, since the product is designed for 4-20mA.). They can even be from German company Alpha-Therm.